People in the United States spend roughly 7.5 billion dollars annually to rent movies and other pre-recorded video programming for private playback at their convenience. Such video programming can be distributed in several forms, such as analog video tapes (and more recently, digital video tape) for playback using a video cassette recorder ("VCR"); analog laser discs for playback on laser disc players; or digital compact discs for playback using either personal computers or else special-purpose compact disc player machines.
Present video playback systems are limited in several respects. Current systems offer relatively limited storage capacity, typically holding the equivalent of a single, feature-length movie on a single disc or tape. Digital video tape offers theoretically greater capacity, if aggressive data compression schemes are used. However, such compression has generally not been used with digital video tapes, because this greatly complicates the implementation of trick mode functions such as slow motion, fast forward, and fast and slow motion reverse.
For example, most of today's VCRs, which use helical scanning, cannot restore and playback the entire video signal if the playback speed is varied either slower or faster than normal. In addition, if the signal is highly compressed, then the loss of even a single bit could result in highly visible artifacts persisting for half a second or longer. Although it is possible to effectively implement trick modes when playing back highly compressed video signals, this requires careful selection of bits to be preserved and bits to be discarded. This type of selectivity is not possible with existing VCR technology without seriously compromising the performance of the VCR player.
Because of this inability to take advantage of high compression ratios, physical storage requirements discourage individuals from maintaining large selections of titles in their own home. Moreover, rental establishments face fierce competition among video titles for limited shelf space, and consumers are often frustrated at being unable to find a copy of the particular titles they seek. A related problem is that current systems cannot conveniently access multiple programs within a user' library, since each program typically resides on a physically separate disc or tape. Therefore, each time a different title or program is desired, the user must physically locate and load the desired tape or disc. In addition, if the selected tape contains more than one program, then the user may also need to search through the tape to find the beginning of the desired program. Clearly, an improved storage and distribution scheme for video programming is desirable.
Recording video programs in the home presents further problems for current technologies. Many people use VCRs to record broadcast or cable presentations for later viewing, in essence "time shifting" a program for perusal at their convenience. Similarly, viewers may watch one broadcast or cable program while simultaneously recording another for later viewing. Read-only discs (such as compact discs and laser discs) are inherently unsuitable for such recording. Consumer VCRs therefore utilize magnetic tape, typically in analog VHS format, and more recently in digital format. However, VCR technology still exhibits important limitations. For example, present videotape recording systems, whether for digital or analog tape, do not support real-time random access; instead, real-time recording and playback proceed in strictly linear fashion.
Moreover, current VCRs do not provide simultaneous, independent read and write access. In other words, a user cannot view a taped program while simultaneously recording another program onto the same tape. For example, if a user wishes to record for later viewing a broadcast or cable presentation using a VCR, the user cannot use the same VCR to enjoy a different movie on tape while the broadcast is being taped. As another example, if a user sets her VCR to record a two-hour television movie starting at 8:00 p.m., and returns home at 8:30 p.m., she cannot simply sit down and watch the movie from its beginning, because her VCR is still occupied recording the broadcast. Consequently, the viewer must either wait until the broadcast ends at 10:00 p.m. (at which point she may be too tired to begin watching a two-hour movie), or else watch the movie out of order, i.e., watch the actual telecast from 8:30 until 10:00 p.m., and replay the taped version of the first half hour afterwards. Neither choice is satisfactory, and an improved VCR with simultaneous read/write capability is therefore desirable.
An additional problem posed by present technology involves managing storage space on tapes containing more than one program. For example, if a user decides to delete one program and store another, one of two situations may exist. If the deleted program is longer than the new program, the new program can be stored in the same "space" on the tape. However, some leftover space exists that is not large enough to store an entire program, and is probably not contiguous with other available space. Thus, it is likely that this amount of storage capacity will be wasted. If, on the other hand, the new program is longer than the deleted program, the new program cannot be stored in its entirety, unless a portion can be stored in non-contiguous space elsewhere on the tape. Consequently, there is a need in the art for an efficient storage management scheme, whereby video programs can be stored, deleted, and accessed with little or no wasted tape storage.
The above discussion demonstrates the need for an improved home video system that supports recording and playback of compressed video programs using an archival storage medium; allows simultaneous recording and playback using the same archival medium; provides efficient storage of multiple programs on a single videotape; supports a full array of trick mode functions; efficiently manages the contents of a video tape or other archival storage medium; and supports real-time random access to video program content, enabling truly interactive playback. As used herein, "video program" data refers to video data and/or audio data.